Ok, so you have a main pc which has bt broadband installed on and a laptop you want to connect it to ?

And the bt modem is now plugged into the router ? And there's RJ45 csable going from one of the free ports into the network card in the main pc.

If the IP address is assigned automatically from BT, then nothing should change at all. If it has to specifiy an IP address then you will need to tell the router this. The only time you need to setup the SSID is when you setup the wireless network.